Rotary valves are well-known in the art, those valves including a valve seating, and a valve disc cooperating with the valve seating, the valve disc being rotatable externally of the valve between an opened and a closed position.
Segmented pipe couplings also are well-known in the art, those couplings including two or more coupling segments having keys that are received within cut or roll-formed grooves in the adjacent ends of pipes, and which are bolted down onto the pipes by traction bolts, the segmented pipe coupling incorporating a sealing gasket that spans the adjacent ends of the pipes, and which is forced into compressive engagement therewith upon tightening down of the traction bolts.
It also is previously known from McClennan U.S. Pat. 5,018,704, issued May 28, 1991 and McClennan U.S. Pat. 5,018,548 also issued May 28, 1991, to form a disc valve as a complete unit, which is positioned between the adjacent ends of pipes, and, which is then secured in that position by a segmented pipe coupling having appropriately configured coupling segments.
Such a rotary valve and pipe coupling combination, however, is of greatest utility when used for coupling metal pipes, and encounters a disadvantage when employed with plastics pipes.
For such a segmented pipe coupling to be secured to the adjacent ends of pipes, it is necessary that the ends of the pipes be grooved for them to receive the securing keys of the respective coupling segments.
While this poses no problem in metal pipes, which are of considerable strength, and which readily can be grooved by cut-grooving or roll-grooving, plastics pipes pose a particular problem in that they are structurally considerably less strong than metal pipes, particularly at the groove required in the plastics pipe in order to accommodate the keys of the coupling segments, that groove commonly having been formed by cut-grooving.
At the cut-groove, the wall thickness of the pipe has been very considerably reduced by the depth of the cut-groove. Particularly in plastics pipe, this represents a major structural weakness in the piping system, unless compensated for by employing plastics pipe having a wall thickness that has been increased in thickness by an amount equal to the depth of the cut-groove.
This, however, results in either an increase in the external diameter of the plastics pipe if the internal diameter is to be maintained at a standard diameter, or conversely, the reduction in the inner diameter of the plastics pipe in the event that an increase in the external diameter of the plastics pipe is not permissible.
If the external diameter of the plastic pipe is to be increased, then, this requires step-down couplings for connecting the pipe to corresponding standard pipe. In the alternative, a decrease in the pipe internal diameter results in a reduction in the flow capacity of the assembled pipe line.
An increase in the wall thickness of plastics pipe becomes necessary when the segmented pipe coupling is employed to join two independent lengths of plastics pipe, which in turn requires the cut-groove in the exterior of the respective pipes to be positioned closely adjacent the end of that pipe.
This, however, presents a source of weakness in the plastics pipe, particularly in the event that the pipe line is subjected to axial bending moments. If the moment is sufficient, this can result in either ripping off of the pipe end in the location of the groove, or, deflection, bending and other distortions of that portion of the pipe that extends between the pipe end and the groove, with a possibility of the pipe pulling out of the segmented pipe coupling, possibly with disastrous consequences.
Clearly, it would be a major advantage if the plastic pipe could continue continuously and without interruption through the segmented pipe coupling.